Buggy code:
public class tree extends JPanel implements KeyListener { public tree ( JFrame parentWindow ) { } protected ImageIcon createImageIcon ( String path , String description ) { <START_BUG> URL imgUrl = getClass ( ) . getResource ( path ) ; <END_BUG> if ( imgUrl != null ) return new ImageIcon ( imgUrl , description ) ; else return null ; } public JMenuBar createMenuBar ( ) { } public void createToolBar ( ) { } public void createPopupMenu ( ) { } public void keyTyped ( KeyEvent e ) { } public void keyPressed ( KeyEvent e ) { } public void keyReleased ( KeyEvent e ) { } public void setArticleSaved ( int i ) { } public int getArticleSaved ( ) { } public void setFileSaved ( int i ) { } public int getFileSaved ( ) { } public JTree getTree ( ) { } public void setFileName ( String s ) { } public String getFileName ( ) { } public JFrame getParentWindow ( ) { } public void enablePaste ( ) { } public void disablePaste ( ) { } public JPopupMenu getPopupMenu ( ) { } public void setMovingNode ( DefaultMutableTreeNode n ) { } public DefaultMutableTreeNode getMovingNode ( ) { } public void setMoveCount ( int i ) { } public int getMoveCount ( ) { } public String getTextPaneText ( ) { } public void setTextPaneText ( String s ) { } public int getNodeCount ( ) { } public void setNodeCount ( int i ) { } private JFrame parentWindow ; private JTree thetree ; private JTextPane textPane ; private Action newAction ; private Action openAction ; private Action saveAction ; private Action saveAsAction ; private Action quitAction ; private Action findAction ; private Action cutAction ; private Action copyAction ; private Action pasteAction ; private Action pasteSiblingAction ; private Action saveArticleAction ; private Action renameAction ; private Action addNodeAction ; private Action deleteAction ; private Action moveUpAction ; private Action moveDownAction ; private Action contentsAction ; private Action aboutAction ; private DefaultMutableTreeNode rootNode ; private DefaultTreeModel treeModel ; private DataInfo item ; private int nodeCount ; private int moveCount ; private DefaultMutableTreeNode previousSelectedNode ; private DefaultMutableTreeNode movingNode ; private int articleSaved ; private int fileSaved ; private String theFile = "" ; private JPopupMenu popup ; private PopupListener popupListener ; void populate ( ) { } public class FindAction extends AbstractAction { public FindAction ( String text , String desc , int mnemonic , KeyStroke accelerator ) { } public void actionPerformed ( ActionEvent e ) { } } public class ContentsAction extends AbstractAction { public ContentsAction ( String text , String desc , KeyStroke accelerator ) { } public void actionPerformed ( ActionEvent e ) { } } public class MyListener implements TreeModelListener { public void treeNodesChanged ( TreeModelEvent e ) { } public void treeNodesInserted ( TreeModelEvent e ) { } public void treeNodesRemoved ( TreeModelEvent e ) { } public void treeStructureChanged ( TreeModelEvent e ) { } } public class MyMouseListener implements TreeSelectionListener { public void valueChanged ( TreeSelectionEvent e ) { } } }

Fix:
URL imgUrl = getClass ( ) . getResource ( ( "//resources" + path ) ) ;